1. Field of the Invention
The invention is directed to the manufacture of metallic products such as sheet, strip, rod, wire or band, especially of difficult to work intermetallic alloys like aluminides of iron, nickel and titanium. Particularly, the invention is directed to a hot rolling operation utilizing an inductive heating processing step and associated process control feedback.
2. Background of the Invention
In the description of the background of the present invention that follows, reference is made to certain structures and methods, however, such references should not necessarily be construed as an admission that these structures and methods qualify as prior art under the applicable statutory provisions. Applicants reserve the right to demonstrate that any of the referenced subject matter does not constitute prior art with regard to the present invention.
Powder metallurgical processes for preparing sheets from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide, are disclosed in commonly owned U.S. Pat. No. 6,030,472, the contents of which are herein incorporated by reference. In such processes, non-densified metal sheets of aluminide are consolidated from a powder by roll compaction, tape casting or plasma spraying. A cold rolled sheet is formed by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness followed by annealing.
U.S. Pat. No. 6,143,241, the contents of which are herein incorporated by reference, discloses a method of manufacturing intermetallic products by a process including cold working and intermediate or final flash annealing.
U.S. Pat. No. 6,166,360, the contents of which are herein incorporated by reference, discloses the use of a combined induction heating and conduction heating process to uniformly heat a part of varying thickness for hot forming and heat treatments such as hardening and tempering.
U.S. Pat. No. 4,782,994, the contents of which are herein incorporated by reference, discloses an apparatus for inline annealing of strip material including a hot press followed by a plate annealer and a field annealing process. A computerized control means provides signals for a strip feeding rate, temperature and pressure of the heated pressure rolls, temperature of the separate inline annealer, and tension on the strip.
Iron aluminides generally require multiple pass rolling operations during which a sheet stock is reduced in thickness. The capital investment required to assemble a rolling line for iron aluminide is substantial. Currently, aluminide stock is processed in a multiple roll rolling line having up to sixty or more rolling operations. For instance, product that has undergone multiple rolling steps is removed from the in-line process and tested off-line. Testing techniques may be non-destructive (i.e., ultrasonic examination) or may be destructive evaluation processes (i.e., sectioning and polishing for microscopic or visual examination). Thus, metallurgical evaluation is made as to the acceptability of the final work product only after completion of the value added processing steps.
Therefore, there is a need to provide a rolling operation for aluminide materials, particularly sheet stock, that reduces the capital investment and provides for inline process monitoring and feedback. Further, there is a need to minimize the number of required passes in a rolling operation for aluminide stock material.